The present invention relates to apparatus and methods for effecting up to full-width ultrasonic bonding on at least one continuously moving web, or work piece attached to a continuously moving web, using ultrasonic bonding apparatus. The invention more particularly concerns apparatus and methods for effecting up to full-width ultrasonic bonding on at least one continuously moving web using rotary ultrasonic bonding.
It is known to bond at least one continuously moving substrate web along up to its full width by constrictively passing the web between multiple rotating ultrasonic horns and a common, multiple repeat, full-width rotating anvil roll. Typically, the anvil roll includes one or more arrays of raised projections configured to bond the web in a predetermined bond pattern. The rotary ultrasonic horns are capable of expressing ultrasonic energy at a bonding surface to ultrasonically bond the web as the web constrictively travels between the rotary ultrasonic horns and the common anvil roll. Representative examples of rotary ultrasonic horns which have been used to bond at least one web are described in U.S. Pat. No. 5,096,532 to Neuwirth et al issued Mar. 17, 1992; and U.S. Pat. No. 5,110,403 to Ehlert issued May 5, 1992.
The consistency and quality of the bond when using such rotary bonding techniques is dependent on the consistency of the force exerted on the web by the combination of the anvil roll and the bonding roll; the time during which the web is being pressed in the constrictive nip which is dependent on, among other things, the operating speed; and the types of materials being bonded. The consistency and quality of the bonds are also dependent on the frequency and amplitude of the vibrations of the ultrasonic horn.
In the above conventional technology, to achieve full-width bonding, the web or webs being acted on are wrapped in surface-to-surface relationship with the rotary anvil over a substantial portion of the circumference of the rotary anvil. Multiple rotary ultrasonic horns used in combination with a common anvil can be acceptable for bonding thin webs along the full width, but webs with thin and thick sections such as diaper webs, which include intermittently spaced fluff pads, are not readily adapted to such wrapping of the rotary anvil. The anvil tends to need longitudinally-spaced reliefs centered on the width of the anvil to allow such fluff pads to pass through the horn/anvil nip. The only way to provide such reliefs under conventional methods is to use a bearer ring, to use a continuous bond line as a bearer, or to cam the horns in unison with the thick-to-thin section transition of the web, into and away from the anvil.
Another problem with the conventional method and apparatus is that positioning more than two horns against a single, common anvil requires the use of multi-repeat anvils. The use of multi-repeat anvils is dictated by the phenomena that only two horns can fit against an anvil at any point on its circumference. The occurrence of any run-out makes getting good bonds on more than one anvil very difficult using multi-repeat anvils.
Adjusting a single horn against a rotary anvil having a single repeat pattern can be accomplished with relative ease, but if the anvil comprises two repeats, making the horn contact both patterns with equal force is more difficult, unless run-out is generally less than 0.0002 inch TIR (Total Indicator Runout). As a result, conventional anvils are costly and not interchangeable.
As used herein, the term xe2x80x9crunoutxe2x80x9d expresses changes in the radius of the rotary anvil roll and/or the rotary ultrasonic horn about the circumference of the respective rotary element.
Conventional methods for rotary bonding include a rotating ultrasonic horn which is mounted in a cantilevered configuration such that the horn is not supported about the surface of the bonding roll. However, such conventional methods have not always been sufficiently satisfactory.
Use of full-width bonding anvil rolls has inherent limitations which adversely affect the bond quality and which in this invention can be at least partially corrected by replacing a cantilever configuration with an in-line or balanced force application which effectively off-sets the effect of application of forces through cantilevered configurations.
In cantilevered configurations, it has been very difficult to maintain the desired degree of consistency and stability of nip force between the bonding rolls and the common anvil roll. As a result, in many conventional methods for rotary full-width bonding, bond quality and/or consistency has been undesirably variable both along the length of the bond region and across the width of the bond region. In addition, processes using cantilevered rotary ultrasonic horns have not been as robust as desired for a manufacturing environment.
When using conventional methods for full-width rotary bonding in such configuration, the bond quality has typically been less than satisfactory along the length of the bond pattern. Such inconsistency in the bond pattern has been due, at least in part, to inconsistent levels of force being effectively applied along the length of respective intermittently applied bond regions of the bond pattern. Typical of such inconsistency is excessive nip loading at such leading edge of the bond region, and insufficient nip loading behind the leading edge of the respective element as the bonding apparatus flexes or deflects in combination with development of the respective bonding region at the nip. Both the excessive nip loading and the insufficient nip loading have resulted in poor bond quality and poor bond consistency.
Under excessive loading, so much energy may be applied to the materials being bonded as to burn through or otherwise excessively soften the materials being bonded, as well as to apply excessive pressure to the softened materials, whereby bonds so formed may be weak, and/or may be uncomfortably harsh to the touch of a wearer""s skin. In the alternative, excessive loading can physically damage, as by tearing, the material being bonded.
Generating ultrasonic bonds depends on the combination of frequency and amplitude of the vibrations, the amount of pressure applied, and the time during which pressure is applied. Under conditions of insufficient loading at the nip, too little pressure is applied to the materials intended to be softened thereby, whereby the amount of energy transferred to the elements to be bonded together is insufficient to develop sufficiently strong bonds.
Conventional methods for full-width rotary bonding have used different approaches to diminish the variations in consistency of the interference. For example, the bonding rolls, anvil roll, and support frames have been precisely machined to minimize run-out in the bonding system.
The above-mentioned difficulties of maintaining desired bond quality and consistency along both the length and full-width of the web become even more acute when bonding at least one continuously moving web using multiple rotary ultrasonic horns. Operation of multiple rotary ultrasonic horns includes movement inherent in the continuous vibration of the horns at a given frequency and amplitude to efficiently bond the web, as well as rotation of the horns along the length of a web which may vary in thickness along the length of the web, thus to impose varying resistance to the nip pressure applied by the combination of each horn and the anvil on the web. Under certain conditions, such vibratory movement of the horn, and variation of web thickness, either alone or in combination, may adversely affect bond consistency and quality in the web.
In addition, where the web advancing through the nip, defined between a horn and the anvil, varies in thickness and/or density, the web can apply a correspondingly varying back pressure on the horn and anvil. The overall result of nip variation, then, can be defined in terms of the combination of the degree of variability in manufacturing and mounting the horn and anvil, as well as the degree of variability in thickness of the web moving through the nip between the anvil and horn.
It is an object of this invention to provide bonding apparatus and methods wherein nip pressure is consistent along the lengths and widths of respective bonding regions, for bonding up to the full width of the web.
It is another object to provide rigid and stiff bonding apparatus for up to full width bonding wherein reduced interference can be employed while achieving an effective level of nip loading at the bonding nip.
It is a further object to provide a method for developing bond consistency between bond regions while attenuating pressure and bond variation internal to the respective bond regions, at up to full width bonding of a respective web.
This invention provides apparatus and methods for developing ultrasonic bonds in combination with a continuously moving web. The apparatus and methods of the invention can be used for developing a bonding pattern extending across up to substantially the full width of a web, optionally multiple webs which may be wholly or in part superimposed one upon the other, using multiple sets of bonding elements spaced along the length of an operations path, each bonding element defining a nip comprising a rotary ultrasonic horn and cooperating rotary anvil. Apparatus and methods of the invention are particularly useful for e.g. ultrasonically bonding selected components of absorbent articles into a web sausage using a rotary ultrasonic horn and cooperating rotary anvil. The bonding apparatus uses multiple rotary ultrasonic horns in combination with the same number of rotary anvils, each anvil generally corresponding in operations width to the width of the cooperating ultrasonic horn, to achieve up to full-width bonding of a web or other substrate material.
In a first family of embodiments, the invention comprehends bonding apparatus disposed along a manufacturing line, the manufacturing line defining at least in part an operations path to be traversed by a web to be acted on by the bonding apparatus, the operations path having a length and a width, and such web having a length and a width. The bonding apparatus comprises support structure supporting the bonding apparatus from an underlying support. The bonding apparatus also comprises a first nip, defined by, in combination, a first set of bonding elements comprising a first rotary ultrasonic horn and a first rotary anvil, and first engagement apparatus bringing the first rotary ultrasonic horn and the first rotary anvil into effective ultrasonic bonding engagement with each other. The first rotary ultrasonic horn and the first rotary anvil are supported from the support structure and rotate in common with each other thereby to convey such web through the first nip. The bonding apparatus also comprises a second nip, defined by, in combination, a second set of bonding elements comprising a second rotary ultrasonic horn and a second rotary anvil, and second engagement apparatus bringing the second rotary ultrasonic horn and the second rotary anvil into effective ultrasonic bonding engagement with each other. The second rotary ultrasonic horn and the second rotary anvil are supported from the support structure and rotate in common with each other thereby to convey such web through the second nip. Each of the rotary anvils has an outer circumference, and an outer circumferential operating surface at the respective outer circumference. The first and second sets of bonding elements are cooperatively disposed at first and second separate and distinct work stations along the length of the operations path, and are disposed at respective first and second different locations across the width of the operations path, so as to act on such web at respective first and second different locations along the width of such web.
The bonding apparatus can be arranged, configured, and timed such that each of the first and second sets of bonding apparatus operate on such web at a common location along the length of such web, optionally thereby to form an uninterrupted pattern of bonding across the width of such web.
Each set of bonding elements can define a bonding width capable of forming a bond pattern of corresponding width in such web, the bonding apparatus including a sufficient number of the sets of bonding elements along the operations path that the sum of the bonding widths of the nips defined by the bonding elements is at least as great as the width of the operations path. The bonding apparatus can be arranged and configured to operate on a such web having a width no greater than the width of the operations path; the bonding apparatus can be further arranged, configured, and timed such that each of the sets of bonding elements operates on such web at a common location along the length of such web, thereby to form an uninterrupted pattern of bonding extending across substantially the entirety of the width of such web.
The bonding apparatus can further comprise a third nip, defined by, in combination, a third set of bonding elements comprising a third rotary ultrasonic horn and a third rotary anvil, and third engagement apparatus bringing the third rotary ultrasonic horn and the third rotary anvil into effective ultrasonic bonding engagement with each other, the third rotary ultrasonic horn and the third rotary anvil being supported from the support structure and rotating in common with each other thereby to convey such web through the third nip. The first, second, and third sets of bonding elements can be arranged at respective first, second, and third separate and distinct locations along the length of the operations path.
The bonding apparatus can include first apparatus for bringing a second web into surface-to-surface relationship with a first such web, after ultrasonic bonds have been formed in such first web at a respective one of the first and second nips, and optionally, second apparatus for bringing a third web into surface-to-surface relationship with at least one of such first and second webs, after ultrasonic bonds have been formed in such first web at a respective one of the sets of bonding elements, and after such first and second webs have been ultrasonically bonded to each other at a respective one of the sets of bonding elements.
The sets of bonding apparatus can be adapted and configured to apply ultrasonic energy to such second web to thereby bond such second web to such first web. Similarly, the sets of bonding apparatus can be adapted and configured to apply ultrasonic energy to such third web to thereby bond such third web to at least one of such first and second webs.
The bonding apparatus can be arranged and configured to apply ultrasonic energy, and therefore to create ultrasonic bonds in a such web, by at least one of the sets of bonding elements overlapping corresponding ultrasonic bonds developed by another of the sets of bonding elements, such that at least one of the ultrasonic horns applies ultrasonic energy to a respective such web at a location whereat ultrasonic bonds have been already formed in such web by the bonding apparatus.
Preferably, at least one rotary anvil has an operating width, at the respective nip, of about 0.6 inch to about 4 inches, more preferably about 1 inch to about 3 inches, and still more preferably about 2 inches.
Ones of the rotary anvils and/or ones of the rotary ultrasonic horns can comprise metal selected from the group consisting of aluminum, iron, monel titanium, and steel, and alloys and mixtures comprising aluminum, iron, monel, titanium and steel.
In some embodiments, the operating surfaces of the rotary anvils comprise arrays of projections thereon extending around the respective circumferences of the rotary anvils, and across entireties of respective transverse widths of the rotary anvils, thereby covering substantially the entireties of respective operating surfaces of respective rotary anvils.
In other embodiments, the operating surface of a respective one of the rotary anvils comprises an array of projections thereon, wherein the array of projections covers a portion but not all of one of the circumference or width of the operating surface of the respective rotary anvil.
Each rotary anvil can comprise a first relatively lesser radius base portion extending about a first portion of the circumference of the respective the rotary anvil, and a second relatively greater radius bonding portion extending about a second portion of the circumference of the rotary anvil. The second radius is preferably about 0.01 inch to about 0.07 inch greater than the first radius.
The bonding apparatus can further comprise a cascading drive wherein timing of the second set of bonding elements, and any subsequent sets of bonding is derived from driving of the first set of bonding elements.
In a second family of embodiments, the invention comprehends apparatus for creating ultrasonic bonds in concurrently advancing webs, thus constructing a composite web having a length and a width. The apparatus comprises apparatus for bringing first and second such webs into surface-to-surface relationship with each other, each such web comprising a number of imaginary segments, each segment of each such web having a segment width comprising a separate and distinct portion of the width of such respective web, and extending along substantially the entire length of such respective web, the multiple segments in each such web being substantially parallel to each other. The apparatus also comprises a number n1 of rotary anvils, each respective rotary anvil having a width substantially equal at least to the width of a respective one of the segments, each respective rotary anvil further having a circumference, and an operating surface defined by an outer circumferential surface, each respective rotary anvil being mounted for rotation about a rotary anvil axis. The apparatus further comprises a number n2 of rotary ultrasonic horns, each respective ultrasonic horn being mounted about a horn axis, each respective ultrasonic horn being paired with a respective rotary anvil to form a respective bonding nip. The ultrasonic horns and the rotary anvils collectively are mounted and configured such that the ultrasonic horns and the rotary anvils can be brought together to define the respective nips therebetween, and wherein the rotary anvils and the ultrasonic horns can rotate in common with movement of such web segments through the respective nips, the number of nips being substantially the same as the number of such web segments.
In a third family of embodiments, the invention comprehends a method of creating ultrasonic bonds in a web having a length and a width. The method comprises transporting the web through bonding apparatus disposed along a manufacturing line, the manufacturing line defining at least in part an operations path to be traversed by the web, the operations path having a length and a width. The transporting of the web includes transporting the web through a first nip, defined by, in combination, a first set of bonding elements comprising a first rotary ultrasonic horn and a first rotary anvil, with the web therebetween, the first rotary ultrasonic horn, and the first rotary anvil being supported from support structure, and rotating in common with each other thereby to convey the web through the first nip. The transporting of the web also includes transporting the web through a second nip, defined by, in combination, a second set of bonding elements comprising a second rotary ultrasonic horn and a second rotary anvil, with the web therebetween, the second rotary ultrasonic horn and the second rotary anvil being supported from the support structure, and rotating in common with each other thereby to convey the web through the second nip. Each of the rotary anvils has an outer circumference, and an outer circumferential operating surface at the respective outer circumference. The first and second sets of bonding elements are cooperatively disposed at first and second separate and distinct work stations along the length of the operations path, and are disposed at respective first and second different locations across the width of the operations path, so as to act on the web at respective first and second different locations along the width of the web. The method also comprises bringing the respective sets of rotary anvils and ultrasonic horns into bonding engagement with each other at respective bonding portions of the respective rotary anvils and ultrasonic horns, and further comprises timing application of the bonding engagements so as to apply at least three of the respective sets of bonding elements to the web at a common location along the length of the web.
The method can include employing a sufficient number of sets of the bonding elements, arranged across the width of the web, to create bonds across substantially the full width of the web.
The method can include drawing the web along the operations path across the respective rotary anvils, and thus through the nips defined between the rotary anvils and respective ones of the ultrasonic horns, at a threading speed of at least about 40 feet per minute.
The method preferably includes drawing apparatus, drawing the web along the operations path across the respective rotary anvils, and thus through the nips defined between the rotary anvils and respective ones of the ultrasonic horns, at a speed of at least about 600 feet per minute, more preferably at least about 1000 feet per minute.
The method can include mechanically loading each set of bonding elements at up to about 400 pounds of pressure per inch linear width across an energy-applying portion of the nip as defined by the respective rotary anvil and corresponding ultrasonic horn.
The rotary anvils each can have a pattern of raised elements on the respective circumferential surface, each respective set of bonding elements developing bonds in the web in accord with the raised elements.
The method can comprise drawing a second web, having a length and a width, into surface-to-surface engagement with a first web at at least one of the respective first and second nips, and employing the respective set of bonding elements at the respective nip to bond the second web to the first web, thereby to define a combination web.
The method can include disposing the second web in surface-to surface engagement with the first web at each of the respective nips, and employing the respective sets of bonding elements at the respective nips to bond the first and second webs to each other.
The method can include employing sufficient number of sets of bonding elements, arrayed across the widths of the first and second webs, to bond the second web to the first web across the entirety of the width defined by the surface-to-surface engagement of the first and second webs with respect to each other.
The method can include drawing a third web, having a length and a width, into surface-to-surface engagement with at least one of the first and second webs after the ultrasonic bonding of the first and second webs to each other, and applying ultrasonic energy to the third web at a third location downstream from the first and second sets of bonding elements, thereby bonding the third web to the combination web.
Ultrasonic bonding can be effected by at least one of the sets of bonding elements overlapping, along the width of the web, with ultrasonic bonding effected by at least one other of the sets of bonding elements, such that at least one rotary ultrasonic horn applies ultrasonic energy to previously ultrasonically bonded portions of the web.
In a fourth family of embodiments, the invention comprehends a method of fabricating a composite web having a length and a width wherein first and second webs are bonded to each other over substantially the entirety of a common width. The method comprises drawing the first and second webs into surface-to-surface relationship with respect to each other over a common width, and thereby defining a web combination. The method further comprises passing the web combination through first and second nips spaced at first and second locations along a length of a manufacturing line, each nip being defined by, in combination, a set of bonding elements comprising a rotary ultrasonic horn and a rotary anvil. The method also comprises bringing each respective set of bonding elements together in defining the respective nips, and correspondingly developing suitable pressure in the nips to create ultrasonic bonds. The method further comprises activating ultrasonic energy in the respective rotary ultrasonic horns, and rotating the respective ultrasonic horns and rotary anvils in common with movement of the web combination through the respective nips, thereby applying pressure to the web combination, and correspondingly creating ultrasonic bonds in the web combination as the web combination passes through the nips, and thereby transforming the web combination into a combination web.
The method can include intermittently applying pressure to the web combination through the respective nips and correspondingly creating longitudinally-spaced intermittent bonds in the web combination at the respective nips, and wherein the bonds created by successive such nips are positioned in registration with respect to each other across the width of the combination web.
The method can include arranging the respective sets of bonding elements across the width of the web combination at respective longitudinally spaced locations with combined effective bonding widths of the respective nips effecting bonding at substantially all locations across the width of the web combination, such that the entireties of the common widths of the first and second webs are bonded to each other across the entirety of the common width of the combination web, optionally along substantially the entire length of that portion of the combination web which has passed through the respective nips, or optionally at longitudinally-spaced locations along the length of the combination web.
The method can include developing bonds along the entirety of the width of the web combination, including width segments projected from only one of the two webs.
The method can include disposing a third web onto the combination web after the ultrasonic bonding of the first and second webs to each other at the first and second locations, ones of the sets of bonding elements applying bonding levels of ultrasonic energy to at least one of the combination web and the third web at locations where the third web overlies the combination web, thereby bonding the third web to the combination web.
The method can include applying ultrasonic bonding energy at successive ones of the sets of bonding elements wherein a subsequent set of bonding elements overlaps a portion of the width of ultrasonic bonding applied by a more upstream set of bonding elements in the manufacturing line, such that at least one of the rotary ultrasonic horns applies ultrasonic energy to previously ultrasonically bonded portions of at least one of the first and second webs.
Similarly, the method can include applying ultrasonic bonding energy at successive ones of the sets of bonding elements wherein a subsequent set of bonding elements overlaps a portion of the width of ultrasonic bonding applied by a more upstream set of bonding elements in the manufacturing line, such that at least one of the rotary ultrasonic horns applies ultrasonic energy to previously ultrasonically bonded portions of at least one of the first, second, and third webs.
The method can comprise deriving timing of the second set of bonding elements, and any subsequent sets of bonding elements, from driving of the first set of bonding elements.
In some embodiments of the method, the rotary anvils comprise first relatively lesser radius portions extending about respective first portions of circumferences of the rotary anvils, and second relatively greater radius bonding portions extending about second portions of the circumferences of the rotary anvils.
The method can include employing a rotary anvil wherein the greater radius is about 0.01 inch to about 0.07 inch greater than the lesser radius.
The first web can have a greater width than the second web, whereupon the method can include bonding the full width of the second web to the first web.